1. Field of the Invention
The invention relates to a stray-light-coupled biometrics sensing module and an electronic apparatus using such biometrics sensing module.
2. Related Art
Recently, portable mobile apparatuses, such as mobile phones, tablet computers and the like, are developed in rising manners and have become indispensable appliances in the life. More particularly, with the development of the network and the electronic commerce requirement, the mobile phone may further be integrated with an authentication function, representing the personal identification, such as that of an electronic identification card, an electronic passport, a consumable chip card and the like. Therefore, in addition to the conventional digital password authentication, it is a future development direction to enhance the software/hardware function of the personal identification authentication according to the biometrics information (e.g., fingerprint) of the human body. The conventional biometrics information includes the fingerprint, palmprint, iris, vein, face and the like. Based on the device price, the difficulty in use and the characteristic stability, the fingerprint identification method is always the most popular method.
The conventional fingerprint sensors are mainly classified into a capacitive sensor and an optical sensor, wherein the maximum drawback of the capacitive sensor is that it cannot be used to sense the wet finger or the sensing surface with the liquid. In addition, this capacitive fingerprint sensor is embedded into an opening of the housing of the electronic apparatus. So, the outlook of the electronic apparatus is affected, and the dust and dirtiness may be left in the gap between the sensor module and the electronic apparatus, and the outlook is further deteriorated.
FIG. 1 shows a frequently seen optical fingerprint sensor 500, which works according to the total reflection principle of light between a fingerprint FP and an optical surface plane (usually a surface plane 512 of a prism 510) in contact with the fingerprint FP, so that a fingerprint image is constructed on an image sensor 530. This sensing principle has the maximum drawback that the dry finger cannot be sensed to have the good continuity texture image, so that the misreading problem occurs when the minutia points are being extracted. Meanwhile, it is also necessary to provide a collimated light source 520 emitting light for the total reflection principle. This also increases the cost and the design complexity.